Carby Spacers

[pullbackandgo]

I was just reading a car mag and there was an ad for performance parts, of which there were carby spacers. Now I just recently re-built my carby and one of the kits i bought(the wrong one) came with a carby spacer. Now I remember my mechanic telling me something along the lines of that depending on the inlet length will vary the torque vs acceleration. But I can't remember which way around it is! Does the inlet length being longer cause the engine to be more torquey?? Or is it the opposite? I know that it is a trade-off between the two.

Why would they list carby spacers in a performance ad? Is it for the reason I have explained above?? Am I talkin 11pm jibberish???

[Colin]

hte spacer gives you more top end and you lose out down low

[Josh]

Interesting.

Colin, what's the physics behind that?

[Colin]

don't know i'm just a dumb mechanic i just know it works

[pullbackandgo]

Okay, this is coming from another dumb backshed mechanic, but from what I've heard, it is because of the extra fuel and air mixture between the valves and the butterfly. The more length in this distance the more fuel and air mixture will be available. This means that when the engine is revving high there is more mixture on tap, so to speak.

Thats one side of the coin, but I'm not sure why the torgue is sacrificed maybe because there is more distance for the mixture to travel at low revs??

This has something to do with why bikes have no torque but accelerate heaps good...I think (correct if wrong)

[Colin]

dumb backshed mechanic not me

[Josh]

This has something to do with why bikes have no torque but accelerate heaps good...I think (correct if wrong)

Uhhh... No.

[pullbackandgo]

care to elaborate?? I was just putting two and two together.... Amyways, is it a worth while mod?

[Colin]

try it

[fritz]

Bikes lack tourque because they dont have a flywheel. - That's my understanding of it???
The tubes connecting the carbs to the engine dont appear to be terribly long in comparison to cars. Especially when you take into consideration that cars have a meaty inlet manifold

[pullbackandgo]

Sorry, me not using my brain at 9.30 in the morn!

Anyways, is it worth doin??

[Josh]

While the inertia added by the flywheel can increase torque marginally, it's real purpose is to smooth out engine vibration, particularly at very low revs. (read: idle)

The real reason why motorcycles lack torque is simply because they are very light vehicles endowed with a very large engines. Why waste the potential for awesome kW at high revs on torque that you don't really need? The engines are specifically tuned for peak power rather than bottom-end grunt by virtue of physical characteristics of the vehicles themselves.

[fritz]

Yikes! - I'd hate to think how bad mine would idle with no flywheel Also, I dont fancy my chances of taking off from rest at 1500rpm with a VERY light flywheel.

[Colin]

wrong josh the bigger/heavier the flywheel the more torque you have but the slower the engine will rev up ie trucks have huge flywheels so they dont stallwhen taking off or going up hills where as a bike uses its clutch cage as the flywheel alowing it to rev up quickly without excessive load on it (as in no fat chicks)

[Josh]

Just reciting what I was taught in TAFE.

Of course the flywheel ads torque but I was always told that it's purpose is to add momentum to the crank in order to smooth out the processes of the engine. Of course engines with massive flywheels such as trucks produce monster torque, but let's not forget the engine needs to be producing monster torque in the first place to rev up the big metal disc!